The IPCC has said: "Following a referral from the force in 2014, the IPCC investigated the force's response to the rape allegation, including whether its decisions and actions were in accordance with local and national policies and guidance.

"The investigation examined the actions of the detective constable who led the investigation and found the officer had actively pursued all lines of enquiry based on the information available and the actions taken were justified and proportionate in the circumstances.

"The detective inspector (DI) overseeing the investigation was found to have sufficiently scrutinised and managed the rape investigation and the detective chief inspector responsible for reviewing the DI's assessment of the investigation, was found to have applied proportionate and appropriate decision-making.

"Due to the sensitive nature of the original investigation, the IPCC will not be publishing its final report".